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Inhaled drug delivery is widely used in the treatment of respiratory diseases. Understanding the deposition mechanisms of dry powder inhalers (DPIs) in different regions of the airway is crucial for inhaler development and prediction of the deposition distribution of drug particles. And the insertion of the inhaler will significantly alter the pattern of airflow in the airway. The main objective of this study is to systematically investigate the distribution and mechanism of aerosol particle deposition in various regions of the inhaler-airway model. Computational fluid dynamics (CFD) was used to simulate the effect of inhalation flow rate on the deposition of drug particles in various regions of the airway. The discrete phase model (DPM) was adopted to track the deposition trajectories of drug particles. Three different inhalation flow rates together with six particle sizes and five particle densities were analyzed. The results indicated that the overall deposition fraction of drug particles gradually increased with particle size and density. The pattern of depositional distribution in other local areas is quite different from the overall pattern except in the oral. The deposition fraction in the pharynx was much larger than in the other local regions, the deposition fractions in the larynx, trachea, carina and bronchi were less than 5 %. The increase in density increases the deposition fraction of particles in various regions throughout the respiratory tract when the inhalation flow rate is 30 L/min. Most of the particles in the oral are deposited on the tongue, and the particles in the bronchus are more distributed in the main trunk, while deeper in the bronchus, particles are also deposited in the bifurcation region. The subject's inhalation posture also affects the local distribution of the airflow. The findings of present study can help to guide the optimization and in vitro-in vivo correlation of DPIs. [Display omitted] • Realistic inhaler-airway model reconstructed. • The distribution and mechanism of particle deposition in various areas are studied. • The effects of inhalation flow and particle parameters were systematically studied. • The results will help guide the optimization and in vitro-in vivo correlation of DPIs. [ABSTRACT FROM AUTHOR]

Population balance methods utilised in multiphase flow simulations mark a significant advancement in computational fluid dynamics. However, existing approaches exhibit shortcomings, such as being prone to inaccuracies or being computationally prohibitive. Addressing these challenges, a recent innovation in closure for the method of moments is the introduction of quadrature based moments methods (QBMM). Discretising a distribution by a number of discrete elements, QBMM facilitate efficient and accurate tracking of density distributions, particularly for particle size distributions (PSD). However, obtaining the full particle size distribution information using these methods requires reconstructing the distribution from a finite set of moments, which is not a trivial step. This study introduces a novel combination of the maximum entropy reconstruction (MER) and QBMM, establishing a robust and rapid framework for the time evolution and reconstruction of PSDs. As proof of concept for this framework, we focus on the direct quadrature method of moments (DQMOM) with spatially homogeneous and monovariate distributions. We show that coupling of MER with DQMOM has numerous advantages. To verify the framework, special cases of constant growth, aggregation, and breakage are considered for which analytical solutions can be found. Furthermore, we show the advantage of using DQMOM with volume-based over length-based distributions, and address numerical as well as theoretical issues. Application of the framework is successfully conducted on the evolution of the PSD from a twin-screw wet granulation dataset, considering all active primary physical mechanisms in a wet granulation process, namely growth, aggregation, and breakage. This showcases the consistency of the proposed framework and underscores its applicability to real-world scenarios. [Display omitted] • Introduce quadrature based moments methods (QBMM) for wet granulation. • Maximum entropy reconstruction (MER) for direct quadrature method of moments (DQMOM). • Ensure exact volume conservation in DQMOM using volume-based distributions. • Predict reconstruction domain boundaries transiently by coupling DQMOM to MER. • Apply the algorithm to an experimental twin-screw wet granulation dataset. [ABSTRACT FROM AUTHOR]

This paper investigates wear characteristics in a dilute phase pneumatic conveying pipe system using a Euler-Lagrange method. Simulations couple computational fluid dynamics (CFD) with the discrete element method (DEM) to analyze three different bend geometries, including two erosion-reducing designs and a standard bend, all with an effective bend radius to pipe diameter ratio (R/D) of 1.5. SiO 2 particles, 1 mm in diameter, are conveyed at gas velocities of 15 to 30 m/s and mass loadings of 1 to 4 kg particle /kg gas. The CFD-DEM predictions were validated against experimental data, showing good agreement in erosion distribution. The study evaluates erosion rates, pressure drops, and particle stressing for the three bends. Results suggest that certain bend designs significantly reduce erosion while slightly increasing pressure drop, although reduced particle-wall erosion may increase the overall particle stressing. The obtained results provide guidance on selecting an appropriate bend design and for potential geometry optimizations. [Display omitted] • Four-way coupled CFD-DEM simulations for more sustainable pneumatic conveying. • Utilization of erosion model by Oka et al. 2005 for quartz against stainless steel. • Significant erosion reduction was observed due to optimized bend geometries. • Analyses of operational parameters and trade-offs for erosion reduction. • Behavior of erosion, pressure loss and particle stress in different bend-geometries. [ABSTRACT FROM AUTHOR]

Hydrodynamic transport is crucial in deep-sea mining engineering for conveying materials. This study investigates the impact of various particle shapes on slurry transport efficiency and flow characteristics at higher concentrations. A numerical method combining computational fluid dynamics (CFD) and the discrete element method (DEM) within the Euler-Lagrange framework is employed to simulate the flow and hydrodynamic properties of graded heterogeneous coarse particles in a deep-sea hydraulic lift pipe. The reliability of the simulations is verified through comparisons, focusing on feed concentration and particle gradation effects on dynamic characteristics and flow patterns. The study quantitatively analyzes concentration distributions under various flow regimes for different particle shapes and conveying concentrations in a vertical pipeline system. Flow characteristics under clogging conditions are described, considering flow transition and concentration distribution. Additionally, conditions for stable transportation are discussed concerning particle forces and transport reliability. [Display omitted] • A coupled CFD-DEM model simulates deep-sea mining hydraulic transport of graded particles. • Higher feed concentration accelerates large particles and slows smaller ones. • Special-shaped particles significantly increase wall shear stress, peaking at 95 Pa. • Radial segregation is pronounced with oscillations in solid volume fraction up to 0.03. • Findings optimize pipeline design for efficient, stable particle transport in deep-sea mining. [ABSTRACT FROM AUTHOR]

In cigarette processing, the challenge is particularly significant during the air classification of tobacco and stems due to their similar characteristics. This paper employs computational fluid dynamics (CFD) combined with the discrete element method (DEM) to analyze factors affecting separation efficiency and improve performance. The results were validated through laboratory and production line experiments at a 1:1 scale. The tobacco (length: 0 mm–4.75 mm, diameter: 0.32 mm) and stem (length: 0–25.145 mm, diameter: 1.51 mm) were modeled based on production samples. Findings suggest that particle feeding speed primarily impacts tobacco loss rate, while inlet air velocity mainly influences stem removal rate. Optimizing the chamber structure in the simulation resulted in a 63.66 % improvement in separation efficiency. Airflow streamlines, particle distribution, trajectory, and collision behaviors were discussed to illuminate motion characteristics. The flexible particle model moderately influenced separation efficiency and collision behaviors. These insights enhance the understanding of particle separation and the design of separation devices. [Display omitted] • The effects of feeding speed, inlet velocity, and mass flow rate are discussed. • Optimizing the device structure improves efficiency by 63.66 %. • Collisions between tobacco particles enhance their state of suspension. • Collisions between stems increase their likelihood of sedimentation. • Flexible models simulate the winding characteristics more accurately. [ABSTRACT FROM AUTHOR]

Pneumatic conveying of mineral particles is widely used in underground roadway material transportation and support. However, the breakage of large particles at bends is inevitable. Based on a coupled Computational Fluid Dynamics (CFD) and Discrete Element Method (DEM) method, the Euler-Lagrange equation was used to investigate the breakage of quartz particles (8 to 12 mm) during pneumatic conveying. By the Tavares UFRJ model, single large particle transport was simulated and the particle breakage was described as preliminary breakage and final breakage. The pneumatic conveying of multiple particles was simulated, and a detailed analysis was conducted on the effects of airflow velocity, particle size, and gravity direction on the particle breakage rate. The results indicated that the particle breakage rate increased with the rise in airflow velocity and particle size. The breakage rate was highest when the direction of gravity was in the negative x-direction and lowest in the negative y-direction. [Display omitted] • The Tavares model was applied to study the breakage of large minerals at the bend. • The airflow velocity has large effect on particle breakage in pneumatic conveying. • The breakage ratios and sizes increase with particle size for fixed airflow velocity. • The particle breakage ratio is the lowest for a horizontal to vertical pipeline. [ABSTRACT FROM AUTHOR]

Cyclones represent a cost-effective solution employed for the separation of particles in gas-solid streams, wherein the enhancement of performance relies on the careful balance between pressure drop and collection efficiency. This study employs Computational Fluid Dynamics (CFD) techniques to numerically assess a large-scale first stage cyclone within a cement kiln cyclone tower. Investigating its reported low collection efficiency, we analyze the impact of geometric modifications aimed at enhancing cyclone performance. The introduction of a dipleg proves to be particularly effective, leading to a substantial increase in collection efficiency and a reduction in pressure drop. The most favorable cyclone configuration demonstrates a remarkable 6 % improvement in collection efficiency and a decrease in pressure drop of approximately 1 mbar. Consequently, particle emissions from the first-stage cyclone are reduced by approximately 30 %, while an increase in clinker production by approximately 100 tons per day is achieved. These findings showcase the potential for significant operational and environmental benefits through optimized cyclone design in cement manufacturing processes. [Display omitted] • CFD techniques for evaluation of large-scale first stage cyclone in a cement kiln. • A diagnosis to explain a poor performance of industrial cyclone based on CFD. • Prognosis proposition for cyclone redesign. • A dipleg improved the efficiency while reducing the pressure drop in cyclone. • The best cyclone presents an emission reduction of 30 %. [ABSTRACT FROM AUTHOR]

This review paper examines the dynamics of snow accumulation on vehicle surfaces and its impacts on vehicle performance and safety. It focuses on the use of computational fluid dynamics (CFD) to model snow ingress in vehicle air intakes and its interactions with sensors in advanced driver assistance systems (ADAS). Central to these studies is the coefficient of restitution (COR), which measures the elastic properties of snow upon collision with vehicle surfaces. The paper provides an overview of various turbulence models, such as large eddy simulation (LES) and Reynolds-averaged Navier-Stokes (RANS), assessing their effectiveness in simulating the aerodynamic fields that affect snow trajectories. It critically reviews existing models and highlights recent experimental studies related to COR of snowflakes based on different impact velocities and particle conditions. The discussion on the practical implementation of these findings in automotive design underscores their importance in enhancing vehicle safety and reliability under extreme weather conditions. [Display omitted] [ABSTRACT FROM AUTHOR]

Concentrated solar energy (CSE) is an excellent source of energy because of the low environmental impacts, high efficiency of power generation, and ease of storage and release when needed. Fluidized beds are considered a good candidate for the receiver of CSE due to their excellent thermal properties, good mixing inside the bed, high interphase energy transfer, particle mobility and convertibility, and inherent flexibility of reactor design and operation. In this study, we attempt to gain a better understanding of fluidized bed systems as CSE receivers, using our computational fluid dynamics (CFD) model to simulate high-energy CSE (254 kW) receiving, storing, and utilizing in the fluidized systems. The capability of the fluidized bed as a high-energy CSE receiver was tested in this study by simulating CSE absorption by a fluidized bed of silicon carbide (SiC). The effect of using encapsulated phase change material (PCM) as the particle in the fluidized bed was also tested to investigate the impact of the bed material properties. Furthermore, continuous cases that used the fluidizing air and SiC particles as heat transfer fluids (HTFs) to utilize the absorbed CSE in a fluidized bed were tested. The results showed the capability of the fluidized bed to be the energy receiver to store and utilize the high-energy CSE. [Display omitted] • A fluidized bed under incident Concentrated Solar Energy (CSE) was simulated using CFD approach. • Our simulation showed, fluidized bed has an excellent capability for CSE absorption and storage. • Using encapsulated phase change material particles, for energy storage, energy loss decreases. • Using particles as heat transfer fluid to receive CSE is an excellent approach. [ABSTRACT FROM AUTHOR]

Gate valves are essential control components in pneumatic conveying systems and often experience erosion on their sealing structures due to impacts from solid particles. The erosion leads to a degradation of the sealing effectiveness and, in severe cases, system malfunction. To address this issue, a numerical model based on computational fluid dynamics (CFD) is developed for the simplified two-dimensional gate valve. The two-way Euler-Lagrange method is utilized to investigate the characteristics of gas-solid two-phase flow and erosion rate. The simulation procedure is verified by comparing the simulation results with experimental data. Results show that the sealing surface separates the free shear layer above the cavity and a low-velocity zone is created on the sealing surface. The particles moving at the downstream bottom are the main particles that impact the sealing surface. The erosion results show that the maximum erosion rate occurs near the top of the sealing surface. And the low-velocity zone reduces the erosion rate within that region. Particle diameter, gas velocity, and valve opening have an important effect on erosion on the sealing surface. The erosion rate increases as the valve opening decreases. The value of the maximum erosion rate increases with particle diameter and gas velocity, and its position changes. Finally, based on the established numerical model, a prediction model for the sealing surface erosion rate is constructed using the surrogate model approach. [Display omitted] • A numerical model for gas-solid flow and erosion of a gate valve is developed. • Most particles that hit the sealing surface are from the bottom of the upstream. • The erosion rate of the sealing surface increases as the valve opening decreases. • The core erosion area is located in the upper region of the sealing surface. • The KRG model accurately predicts the wall erosion rate. [ABSTRACT FROM AUTHOR]

Continuous deposition of workplace pollutant particles on lung airways during respiratory actions seriously threatens the lung health of persons performing tasks in polluted environments. This study aims to analyze the exhalation-driven deposition of fine and coarse occupational pollutant particles in polydisperse form. Computer simulations are conducted to study the patterns of deposition of grain dust, coal fly ash, and bituminous coal particles. Key findings include the observation of early emergence of secondary flows in the real model, a notable shift in deposition patterns towards the post-bifurcation zones, and influence of physical activity intensity on particle deposition. Additionally, deposition primarily occurs near cranial ridge during inhalation, while exhalation leads to deposition in pre- and post-bifurcation zones. PM2.5 deposition is minimal and random in idealized model but becomes more significant and consistent in real model. This research underscores the increased risk of lung diseases for workers in polluted environments during vigorous activity. [Display omitted] • Analysis of exhalation-driven deposition informs pollutant health risks. • Active physical conditions increase deposition. • Deposition comparison of fine (PM2.5) and coarse (PM2.5–10) particles. • High density particles influence lungs health more. • Gravity impact: strong at low flow, weak at high flow when normal to gravity. [ABSTRACT FROM AUTHOR]

The continuum and discrete phase interaction could significantly affect the inhaled particle's transport behaviour. The accurate analysis of continuum and discrete phase interaction needs computational fluid dynamics (CFD) and Discrete Element Method (DEM) simulation, which is computationally expensive. Therefore, this study aims to develop a novel machine learning (ML) prediction model from CFD-DEM data to predict pharmaceutical aerosol transport in airways accurately. This study uses the CFD model for the continuum and DEM for the discrete phases. A soft sphere approach was used to calculate the overlap of the colliding particles. Proper validation was performed to ensure the accuracy of the present model. The CFD-DEM model analysed the particle transport in an idealised and realistic airway model, and different methods were used to analyse the transport behaviour. As the flow rate increased from 15 to 60 lpm, the deposition efficiency (DE) significantly improved due to particle interaction, rising from 20 % to 42 % without interaction and from 50 % to a remarkable 76 % with interaction, demonstrating the critical role of particle interaction in enhancing DE across varying flow rates. During the particle-particle interaction, a stagnation point and a high-pressure zone were observed at the airway model's carinal angle. Finally, a ML prediction model is developed from CFD-DEM data, which accurately predicts the pharmaceutical aerosol deposition in airways. The ML prediction model predicts the deposition pattern for different flow rates and particle sizes without CFD-DEM simulations. The present findings and more case-specific investigation would advance the knowledge of aerosol transport in airways and benefit more efficient targeted drug delivery devices. [Display omitted] • An advanced CFD-DEM-ML model for particle transport in airways; • Spring constant significantly influences the flow fields; • Deposition efficiency increases with the flow rate and particle diameter; • Particle-particle interaction significantly increase with the spring constant; • Deposition efficiency is significantly higher at the upper part of the airway. [ABSTRACT FROM AUTHOR]

Static mixers could promote the particle mixing in industries. Experimental and numerical investigations of particle mixing and flow characteristics in the riser with static mixers are carried out. The instantaneous microscopic characteristics and energy loss in Kwerk-type static mixer (K-KSM) are evaluated by Computational Fluid Dynamics coupled with Discrete Element Method (CFD–DEM). A more suitable calculation method is proposed, which utilizes particle coordinates and the coordination number of central particles to calculate the instantaneous mixing degree of particles (P K). The P K , Residence Time Distribution (RTD) and collision correlation are analyzed at different superficial gas velocities (U g) and mass flow rates (M s). The results show that the performance of K-KSM is superior to that of KSM under current conditions. Back mixing and aggregation phenomena are eliminated at U g > 5 m/s and M s < 1.73 g/s, and the recommended regimes are U g ≥ 6.0 m/s and M s < 1.5 g/s. [Display omitted] • The particle characteristics inside a riser with the Kwerk elements are analyzed. • The images of discrete particles in a fluidized state are identified by CNNs. • The transient mixing correlation of two particles is evaluated. • A suitable method for calculating the mixing of discrete particles is proposed. [ABSTRACT FROM AUTHOR]

The gas-to-metal ratio (GMR) is considered an important parameter in the gas-atomization process for producing metal powders. Consequently, correlations for estimating the mass median particle size (d 50) of powders use GMR as the main parameter. In an industrial setup, it is not easy to measure the melt flowrate to ascertain the GMR. Hence, in this study, we develop a theoretical approach to estimate the melt flowrate and measure it in a pilot setup. Both our theoretical and computational fluid dynamics approaches are in good agreement with the measurements. We then conduct a parametric study to elaborate the effect of certain parameters on the melt flowrate. We believe that the theoretical approach presented here will help to quickly estimate the powder size (d 50) expected from a gas-atomization system. This will help to correctly choose geometric and operating parameters to reduce the spread in powder size distribution in an actual application. [Display omitted] • Molten metal flowrate in a gas-atomization system is an important factor in determining the powder size. • Transient metal flow in a gas-atomization system is analysed using CFD analysis and a theoretical model. • Good agreement is observed for computed melt flowrate with experimental data. • Parametric study indicates promising ways to reduce spread in powder size distribution. [ABSTRACT FROM AUTHOR]

Polydisperse particle feed into centrifugal slurry complicates hydraulic performance and wall erosion but is poorly understood. This paper presents a numerical study of a centrifugal slurry pump, focusing on the effect of particle size distribution (PSD) using the combined computational fluid dynamics and discrete element method (CFD-DEM). It incorporates rigid impeller rotation and wall erosion. On this basis, the hydraulic and erosion model validity is verified by clear water performance and jet erosion test, respectively. Additionally, this CFD-DEM model is compared with the dense discrete phase model (DDPM), demonstrating more precise erosion prediction as its fully resolved particle-particle interactions. Generally, total pump erosion severity intensifies when the PSD is broadened. Compartment-wise, it indicates the necessity of tailoring flow structure to enlarge drag force, therefore, mitigate particle aggregation in the impeller. This in-house CFD-DEM model is promising for addressing particle-fluid flow problems in centrifugal pumps or coupling with data driven method. [Display omitted] • Erosion characteristics to particle-fluid interaction force is elaborated. • Particles accumulate at the trailing side of blade in rotation of impeller. • Increment in particle size distribution (PSD) intensifies the total pump erosion. • Compartment-wise erosion is greatly influenced by the equivalent particle size. [ABSTRACT FROM AUTHOR]

This paper introduces a new mesoscale approach for considering local fluctuations of powder bed characteristics in laser powder bed fusion (PBF-LB/M) simulation, bridging the gap between computational fluid dynamics (CFD) and homogenized mesoscale models. Gusarov and Sih's models for laser heat input and powder bed thermal conductivity were applied to local powder bed elements (PBE) to capture characteristics in the powder bed. Discrete element method (DEM) simulations of the recoating process generated a representative powder bed and determined local porosity values. These values informed local optical thicknesses and thermal conductivities, providing insights into heat transfer in PBF-LB/M. Single-track test simulations showed melt pool sizes matched best with homogenized parameters. The PBE-based approach resulted in smaller melt pools and revealed asymmetries in heat distribution due to varying powder bed characteristics, highlighting the need for accurate powder bed modeling. This mesoscale approach offers an efficient, time-saving alternative to CFD simulations. [Display omitted] • A novel mesoscale approach accounts for local fluctuations in PBF-LB/M powder bed. • The recoating process was simulated using DEM to determine local porosity values. • Model for heat source and heat conductivity based on porosity were used locally. • Homogenized values closely matched experimental results. • The local approach showed smaller and asymmetric melt pools. [ABSTRACT FROM AUTHOR]

Gas-solid two-phase flow characteristics in a 90° bend within a pneumatic conveying system are critical for design and performance optimization, impacting conveying efficiency and system safety. Electrical Capacitance Volumetric Tomography (ECVT) and Computational Fluid Dynamics (CFD) simulations were employed in this study to investigate the flow characteristics in the bend. The ECVT system for bends was validated through static tests. A setup with a 36 mm inner diameter was constructed for high-speed 3D imaging of 0.9 mm quartz particles. Flow patterns, solid-phase concentration, particle velocity spectra, and mass flow rate were analyzed under various gas velocities. The Euler-Lagrange method and SST K-ω model were used to simulate particle flow and pipe wall erosion numerically. Results indicate diverse flow patterns across different gas velocities, where moderate turbulence enhances efficiency and limits erosion. This study offers an experimental basis for predicting and controlling particle motion, providing scientific guidance for optimizing pneumatic systems. [Display omitted] • 3D imaging of a 90° bend was achieved using a 32-electrode ECVT sensor. • Solid concentration, particle velocity, and mass flow rate were analyzed. • Turbulence effect of particle flow in a 90° bend was investigated experimentally. • Euler-Lagrange and SST K-ω models validated experiments and assessed wall erosion. [ABSTRACT FROM AUTHOR]

We implemented fully resolved CFD–DEM simulations to study the rheological behavior of suspensions. Although research in this field mainly uses 2D or 3D simulations to achieve this purpose, we proposed a semi-3D model. By semi-3D models, we mean that the simulation domain contains only one layer of particles in the 3D case. Comparing results with 3D simulations revealed that this approach could significantly decrease the simulation cost while maintaining reasonable accuracy. Furthermore, we selected the Krieger–Dougherty and the Phillips models to validate the viscosity and particle migration in our simulations. We considered different volume fractions of solid particles with two different particle sizes to ensure the accuracy of our model. After successful validation, we used the fully resolved field data of shear rate and vorticity to consider the physics of particular migration in more detail. Our results confirm that our developed model could work as a particle–fluid digital twin system. [Display omitted] • Developing a fully resolved CFD–DEM model to consider the suspension behavior. • Proposing and validating a semi-3D model to decrease the simulation costs while maintaining reasonable accuracy. • A comprehensive consideration of the physics of shear-induced particle migration in the rheometer. • Studying the effects of different volume fractions on suspension viscosity. [ABSTRACT FROM AUTHOR]

Grinding process is a unit operation with various purposes, such as milling, dispersion, and surface modification, and is an indispensable process in various industrial fields, such as food, pharmaceuticals, and cosmetics. Solid feed materials for milling have different physical properties such as strength, hardness, and particle size. Therefore, various types of mills are used depending on the material and the purpose of the milling. A cutter-type disk mill consists of disk-shaped rotating blades and fixed blades, and the rotating blades cause shearing force to the raw material. Therefore, they are used to crush solid materials such as resins, coffee beans, and rice, which are difficult to crush with a simple impact. Cutter-type disk mills are considered particularly effective for grinding plastics. However, it is necessary to optimize the geometry and operating conditions of the mill. This study aimed to evaluate the grinding performance of different blade geometries and particle physical properties in the cutter-type disk mill and to identify the melting factors of resins in the mill. To calculate the effect of the blade geometry and particle properties, the discrete element method (DEM) coupled with the computational fluid dynamics (CFD) and a breakage model was employed to simulate plastic particle breakage. Simulations were performed under conditions where the geometry of the grinding blade and particle physical properties were different. When using the model with angled blades, particle distribution had specific peak position and particles were intensively grinded in this region. On the other hand, the model with radial blades did not have a distribution peak and resulted in strong force and rapid grinding. In addition, it was confirmed that materials which likely to melt in the mill changes depend on the blade shape. Our results show that it is possible to evaluate the grinding performance under the different equipment conditions and with different particle properties, as well as the particle behavior inside the equipment, and that it is effective in improving the process. [Display omitted] • The DEM-CFD with a breakage model was applied to a cutter-type disk mill. • The effect of blade shapes and particle properties on grinding performance was evaluated. • Blade shape greatly affects the particle behavior in the mill. • Materials which tend to melt changes depend on the blade shape. [ABSTRACT FROM AUTHOR]

In fluidized bed reactors, uniform distribution of gas and solids is critical to achieve the desired hydrodynamic and kinetic performance. For FCC units, Technip Energies uses a proprietary distributor design to terminate both reactor risers and spent catalyst lift lines to distribute the exiting gas-solid stream into a fluidized bed. In Technip Energies' Resid FCC unit, air and spent catalyst are distributed from an upward flowing stream into a catalyst bed for coke combustion on catalyst. Proper distribution is key to achieve a uniform coke burn and an even temperature profile throughout the bed. In PropyleneMax™ Catalytic Cracking (PMcc™) technology, the reactor riser also terminates in a fluidized bed, requiring proper distribution of the hydrocarbon vapor and solid mixture into the reactor bed, which is key to providing adequate contact for further cracking to valuable products. This paper discusses Technip Energies' gas-solid distribution technology and the recent work performed to develop an improved distributor for use as a riser termination device in both the PMcc reactor and the RFCC regenerator to achieve improved performance. The use of CFD modeling to screen and evaluate the initial concepts and optimize the final selected concept are presented here. The performance matrices used to quantify the benefits of the optimized distributor design with respect to the existing one in the reactor application are highlighted, showing the benefits of improved gas solid distribution on hydrodynamic and kinetic performance. The paper presents a systematic approach to develop a novel industrial device using physics-based computational tools. [Display omitted] • Systematic approach adopted to optimize gas solid distributor design. • Development built on existing designs experience, cold flow testing and using CFD. • Successfully modeled gas solid distribution in an industrial fluidized bed reactor. • Effectively screened conceptual design using computational modeling. • Improved design indicates reduced streaming and improved vapor/catalyst contact. [ABSTRACT FROM AUTHOR]

Bubble-particle detachment induced by turbulence is the primary factor for the low recovery of coarse particles, which has attracted much attention in recent years. The prevailing centrifugal detachment theory has achieved broad consensus. However, due to the complexity of bubble-particle aggregate motion in the turbulent field, the influence of turbulence intensity on bubble-particle detachment mechanism remains unclear. In this study, a controlled rotating vortex was generated using a custom-made fluid channel to systematically investigate the effect of turbulence intensity on bubble-particle centrifugal detachment. Firstly, detachment behaviours of bubble-particle aggregates were captured using high-speed cameras, followed by flow field visualization of bubble-particle detachment processes using Computational Fluid Dynamics (CFD). Experimental results reveal three typical detachment modes of bubble-particle aggregates in the confined vortex: fluid shear, bubble oscillation, and particle centrifugal motion, with particle centrifugal detachment becoming dominant with increasing turbulence intensity. This shift is attributed to changes in turbulence intensity directly affecting the trajectories of bubble/aggregates and indirectly influencing the detachment mode of bubble-particle. Compared to low turbulence intensity, bubble-particle aggregates exhibit smaller rotational radii under high turbulence intensity, reducing the probability of fluid shear and bubble oscillation detachment by mitigating the influence of high-speed shear zones at the top of the cavity. Conversely, particles located at the edge of aggregates are more susceptible to acceleration by sidewall flow fields, favouring detachment through particle centrifugal motion. Moreover, unlike traditional centrifugal detachment theories, particles do not merely undergo independent circumferential motion on the bubble surface but participate as a whole with bubbles in centrifugal motion governed by vortices. These findings are expected to provide fundamental insights into the bubble-particle detachment mechanism in turbulent fields. [Display omitted] • Investigated the effect of turbulence intensity on the bubble-particle detachment. • Used the overlapping grid method to simulate the bubble-particle detachment process. • Investigated the mechanism of flow field action in bubble-particle detachment process. • A new mechanism of bubble-particle centrifugal detachment was proposed. [ABSTRACT FROM AUTHOR]

To overcome the problems of gas release, energy waste and pipeline leakage of dust erosion wear caused by the fluctuation of the by-product gas pressure in iron and steel enterprises, a 3D mathematical model of a by-product gas pipeline network was constructed in this study. Multi-condition numerical simulation analysis and spatiotemporal pressure fluctuation prediction modelling were also conducted. Firstly, the 3D mathematical model of a by-product gas pipeline network, with an error < 10%, was established by using computational fluid dynamics. Secondly, numerical simulations were conducted under multiple working conditions to study the pressure fluctuation law of the pipeline network and the erosion wear of the pipe wall. Finally, a rapid, accurate, adaptable prediction model was constructed using a spatiotemporal graph convolutional gated recurrent unit method with a combination of the numerical simulation data and pressure fluctuation law. The pressure fluctuation of the by-product gas pipeline network after a change in the blast furnace flow could be predicted in <2 s and the mean absolute percentage error of the prediction was < 2.6%. [Display omitted] • A 3D mathematical model of by-product gas pipeline network was constructed. • The characteristics of the by-product gas transmission in pipeline network were revealed. • The dust particles erosion wear on the pipe wall under different pressure fluctuations was studied. • The law of the pressure fluctuations in the by-product gas pipeline network was work out. • An accurate spatiotemporal prediction model on the pressure fluctuations was constructed. [ABSTRACT FROM AUTHOR]

We present a novel hybrid multi-scale model, referred to as "discrete magnification lens" method, which utilizes a computational fluid dynamics coupled to discrete element method (CFD-DEM) approach within a specific region of interest in a two-fluid model (TFM) simulation. We applied the discrete magnification lens to the crossing jet problem, where the TFM fails due to lack of considering bi-modal velocity distribution in its formulation. It was observed that adopting the discrete magnification lens, can effectively alter the non-physical behavior of the TFM to obey the behavior seen from CFD-DEM simulations. Moreover, the ability of the discrete magnification lens in reproducing particle clusters and improving the TFM predictions in case of unbounded fluidization simulations was further shown. We found that the discrete magnification lens can effectively enhance the TFM predictions in a complex fluid-particle system while requiring less numerical costs compared to the full-scale CFD-DEM simulations. [Display omitted] • A novel hybrid multi-scale model by concurrently coupling TFM and CFD-DEM. • Speedup balance versus accuracy by leveraging the benefits of both TFM and CFD-DEM. • The DML corrects the non-physical behavior of TFM in crossing jets problem. • The DML is capable of reproducing the particle clusters in unbounded fluidization. [ABSTRACT FROM AUTHOR]

The commercial-scale DeNOx catalyst cartridge coupled with filter bag have been developed for the removal of fine particulate matter and nitrogen oxides (NOx) in flue gases. The DeNOx catalyst cartridge coupled filter bag is made up of a microporous PTFE (polytetrafluoroethylene) membrane/impregnated polyimide fiber needle-punched pleated filter bag designed for the removal of ultrafine particulates, along with a pellet selective catalytic reduction catalyst-filled cartridge for the removal of NOx. V 2 O 5 -MoO 3 /TiO 2 catalyst was used as the DeNOx catalyst. The distribution of cleaning air velocity inside the DeNOx catalyst cartridge-coupled filter bag, which is injected with compressed air from the high-volume low-pressure (HVLP) pulse injector to remove the deposited dust cake from the surface of the filter bags during pulse-jet cleaning, was confirmed using computational fluid dynamics (CFD). The particulate removal and dust cake dislodgement characteristics of the DeNOx catalyst cartridge coupled filter bag were tested in a commercial-scale filter bag test unit under conditions simulating fossil fuel combustion flue gas. The commercial-scale DeNOx catalyst cartridge coupled filter bag was 165 mm in diameter, 2000 mm in total length, and contained approximately 12 kg of DeNOx catalyst- filled cartridges. Nine commercial-scale DeNOx catalyst cartridge coupled filter bags were installed in the commercial-scale filter test unit. The experimental conditions were as follows: flue gas temperature 200 °C, flue gas flow rate 3000Nm3/h, NO, SO 2 , and particulate concentration in inflow flue gas 200 ppm, 7 ppm, and 5000 mg/Nm3 respectively, resulting in different values of filtration velocities. The efficiency of bag cleaning and intervals, overall collection efficiency, fractional efficiency, and filter quality were investigated. The average bag cleaning efficiency and overall collection efficiency were 95.5%, 91.5%, and 83.3% at filtration velocities of 0.8, 1.0 and 1.2 m/min, respectively. The corresponding values for overall collection efficiency were 99.9%, 99.5%, and 98.2%. So, both bag cleaning efficiency and overall collection efficiency decreased with increased filtration velocity. The present study confirmed that DeNOx catalyst cartridge coupled filter bags have relatively higher bag cleaning efficiency, collection efficiency, and filter quality for challenging fossil fuel combustion flue gas. Particularly, the fractional efficiency for micron-sized particles was considerably higher at lower filtration velocities. [Display omitted] • DeNOx catalyst cartridge coupled filter bag was able to contain a large amount of catalyst. • Particulate removal characterstics were studied in fossil fuel combustion conditions. • DeNOx catalyst cartridge coupled filter bags show higher efficiencis in removing fine particulates. [ABSTRACT FROM AUTHOR]

Non-spherical particles are prevalent in both natural environments and industrial processes, yet most prior investigations have primarily focused on exploring the behavior of spherical particles. This study employs computational fluid dynamics coupled with discrete element method to investigate the fluidization characteristics and gas-solid interactions in bubbling fluidized bed with non-spherical particles. Following model validation, this study examines bubble dynamics, particle orientation, and particle motion in the system. The findings reveal notable differences between systems containing spherical and non-spherical particles. Specifically, the maximum height attained by bubbles in a non-spherical particle system exceeds that of a system comprising spherical particles. During bubble generation, particle velocities are notably elevated in the upper region of the bubble, while during bubble collapse, particle velocities are higher beneath the bubble. Moreover, cylindrical particles exhibit a tendency to align horizontally at the base of the bed. [Display omitted] • CFD-DEM is adopted to investigate non-spherical particle fluidizing system. • Bubble behaviors are discussed to reveal flow characteristics. • Particle characteristics are investigated to reveal fluidization patterns. [ABSTRACT FROM AUTHOR]

Accurately predicting gas pressure drop in packed beds is challenging in various industrial processes due to the size dispersity of bed particles. The original Ergun equation has been widely used for predicting gas pressure drop in packed beds of monosized spherical particles. Here, we aim to evaluate its prediction accuracy for non-monosized spherical particle beds and propose a modified Ergun-type correlation to consider involved particle-size-dispersity effects. Specifically, we focus on conditions where the tube-to-particle diameter ratio is larger than 14, and the particle Reynolds number, R e p , ranges from 26 to 561. An experimentally validated numerical approach that couples computational fluid dynamics and the discrete element method is used to obtain the gas pressure drop for various beds, showing that the original Ergun equation (with the Sauter mean diameter, d 32 , a common choice in both academia and industry, used as the average particle diameter) yields a predication discrepancy of up to 30%. Accordingly, we propose a novel correlation by using different particle sizes in different terms, revealing the distinct physics of the flow past a sphere in different regimes. In the inertial term, the use of d 32 is reasonable as it considers both volume and surface area of the particles, analogous to the corresponding body and surface forces on the sphere in this regime. In the viscous term, however, the surface-diameter mean, d 21 , which emphasizes particle surface area and geometric effect, is used because it describes the dominant skin frictional surface force in viscous flow. The modified Ergun equation demonstrates improved predictions for bidisperse packed beds by reducing the largest discrepancy to 4%, and can be applied to polydisperse beds as well. Moreover, the proposed correlation aligns well with the original Ergun equation, i.e., the monosized limit, in the investigated R e p range. [Display omitted] • Ergun equation shows limited prediction accuracy for non-monosized packed beds. • It overlooks dense packing (or low porosity) effects in non-monosized packings. • A modification is proposed by using different particle sizes in different terms. • The modified Ergun equation improves prediction, reducing discrepancy to under 4%. [ABSTRACT FROM AUTHOR]

Reliable estimation of the viscosity and rheology of dense suspensions formed from non-spherical particles is of high importance for studies of many natural and industrial processes. Still, the complexity of underlying physics makes predicting the viscosity of such suspensions a challenging task, resulting in a lack of models capable of doing so for general suspensions. In this work, we present an approach based on a combination of the computational fluid dynamics (CFD) and discrete element method (DEM) developed for arbitrarily shaped particles and use it to predict viscosity of dense suspensions of spheres, rods, and glitters. Simulation results are compared to available experimental data and commonly used engineering correlations. The developed model can reliably predict suspension viscosity in a wide range of solid volume fractions and particle shapes. The simulations with spherical particles also reveal a shear-thickening trend at increased shear rates, which corresponds to the experimentally observed non-Newtonian behavior. [Display omitted] • Open-source CFD-DEM code is extended to allow for simulations of dense suspensions. • A new "virtual mesh" concept for DEM with irregular particles is presented. • The framework estimates the dense suspension viscosity within 5% accuracy. • The predicted shear thickening qualitatively agrees with experiments. • The source code and simulation settings are publicly available. [ABSTRACT FROM AUTHOR]

Previous hydrocyclone optimizations often overlooked crucial objectives interactions, thereby weakening the overall system performance. This study presents a framework that integrates meta-heuristic algorithms with preference-informed decision-making to simultaneously optimize key performance objectives. Meta-heuristics identify comprehensive Pareto-optimal sets, while preference-informed decision-making evaluates each solution's overall separation performance according to specific separation preferences. Supported by computational fluid dynamics, the study quantifies the trade-off between optimal overall separation performance and pressure drop, enabling the attainment of optimal overall separation performance at any pressure drop within the Pareto-optimal set. Among the evaluated algorithms, the strength Pareto evolutionary algorithm 2 (SPEA2) stands out for its exceptional diversity and convergence. With this framework, the study circumvents excessive compromises on neglected but crucial objectives, especially highlighting the significant adverse effects of overlooking water split or cut size. Overall, this study provides an integrated approach for developing energy-efficient hydrocyclones that maximize overall separation performance tailored to specific separation requirements. [Display omitted] • Optimizing four objectives mitigates the loss in overall performance compared to two. • SPEA2 generates a more well-distributed Pareto optimal set than other algorithms. • Both preferred separation performance objectives and overall performance improve. • A moderate preference for the weighting ratio of water split enhances the cut size. [ABSTRACT FROM AUTHOR]

A novel graphical processing unit-based discrete element method solver is introduced to improve stability, performance, and provide seamless integration into commercial or open-source computational fluid dynamics software. A key innovation is eliminating a need for network communication between solvers, which was previously required for cross-platform coupling. This is accomplished by a direct coupling method that employs dynamic-linked libraries. Furthermore, the solver optimizes memory usage by streamlining the particle-cell search algorithm by eliminating the cells' searching grid. This ensures the solver is compatible with a wide range of mesh types, providing high geometric flexibility. The approach simplifies the simulation process by directly incorporating computational fluid dynamics mesh information into the discrete element method solver. The performance analysis indicates about sixteen times boost in computational speed compared to benchmark central processing unit-based solvers. The solver's compatibility with polyhedral meshes, a vital advantage for complex geometries, is tested against a referenced study regarding the simulation of an immersed-tube fluidized bed. [Display omitted] • A GPU Discrete Element Method solver coupled to ANSYS Fluent with a DLL file. • Particle velocity and volume fraction against experimental fluidized bed data. • Presented solver shows 2.57 factor speed increase compared to prior GPU coupling. • Solve demonstrated with flexible polyhedral mesh. [ABSTRACT FROM AUTHOR]

The deposition of graphite dust poses significant challenges to the helium turbines in high-temperature gas-cooled reactors. In this study, FLUENT, a Computational Fluid Dynamics (CFD) program was used with a discrete-phase model and a random-walk model to calculate the trajectories of particles (assumed spherical). Considering the interactions between particles and the wall as well as the resuspension effect of the fluid, a particle-deposition model was established and coupled to the flow-field calculations of blades with film cooling using user-defined functions. The influence of different deposition models, particle diameters, and blowing ratios on deposition were investigated. The results show rebounding and resuspending particles significantly affect the particle-deposition rate and its distribution. With increasing particle diameter, the deposition rate initially increases and then decreases. The influence of blowing ratio on deposition is complex; as the blowing ratio is increased, the deposition rate of small particles increases, while that of large particles decreases. [Display omitted] • The motion of graphite dust in helium turbines has been studied. • The deposition and resuspension of particles on the turbine wall are investigated. • The coupling effect of film cooling and graphite dust motion is considered. [ABSTRACT FROM AUTHOR]

The maximum efficiency inlet velocity (MEIV) serves as the upper limit for the inlet velocity that defines the separation efficiency in cyclone design and operation. In this paper, a combination of numerical and experimental methods is used to study MEIV. Experimental findings indicate that the MEIV is 22 m/s for a median particle size of 12.39 μm (coarse powder) and 35 m/s for a median particle size of 2.93 μm (fine powder). Meanwhile, the amount of escaped fine powder is reduced by 25% compared to that at an inlet velocity of 22 m/s. Computational fluid dynamics (CFD) simulations have shown that the inconsistency between tangential and axial velocity growth of inlet velocity with respect to various powder diameters can explain this phenomenon. As the inlet velocity increases, the peak axial velocity exhibits a stepwise increase. When the peak value remains constant, the peak width increases. This phenomenon is called stagnation of the axial velocity. During the axial velocity stagnation step, the residence time of back-mixed particles vary. In contrast, the tangential velocity increases linearly with the inlet velocity, resulting in an enhanced secondary separation of the inner vortex. Both factors hinder the escape of fine particles due to entrainment by a rapid upward airflow. The inlet velocity range corresponding to the stagnation step of the fine powder is larger than that of the coarse powder. Therefore, the MEIV of the fine powder is higher. [Display omitted] • The ceiling of inlet velocity in a cyclone varies with the particle size. • It is inconsistent that tangential and axial velocity growth of the inlet velocity. • The inconsistency is one of the physical mechanisms of the MEIV. • Stagnant axial velocity growth of the inlet velocity reduces the fine particle escape. [ABSTRACT FROM AUTHOR]

Inside fluidized bed reactors, gas–solid flows are very complex: multi-scale, coupled, reactive, turbulent and unsteady. Accounting for them in an Euler-nfluid framework induces significantly expensive numerical simulations at academic scales and even more at industrial scales. 3D numerical simulations of gas–particle fluidized beds at industrial scales are limited by the High Performances Computing (HPC) capabilities of Computational Fluid Dynamics (CFD) software and by available computational power. In recent years, pre-Exascale supercomputers came into operation with better energy efficiency and continuously increasing computational resources. The present article is a direct continuation of previous work, Neau et al. (2020) which demonstrated the feasibility of a massively parallel simulation of an industrial-scale polydispersed fluidized-bed reactor with a mesh of 1 billion cells. Since then, we tried to push simulations of these systems to their limits by performing large-scale computations on even more recent and powerful supercomputers, once again using up to the entirety of these supercomputers (up to 286,000 cores). We used the same fluidized bed reactor but with more refined unstructured meshes: 8 and 64 billion cells. This article focuses on efficiency and performances of neptune_cfd code (based on Euler-nfluid approach) measured on several supercomputers with meshes of 1, 8 and 64 billion cells. It presents sensitivity studies conducted to improve HPC at these very large scales. On the basis of these highly-refined simulations of industrial scale systems using pre-Exascale supercomputers with neptune_cfd, we defined the upper limits of simulations we can manage efficiently in terms of mesh size, count of MPI processes and of simulation time. One billion cells computations are the most refined computation for production. Eight billion cells computations perform well up to 60,000 cores from a HPC point of view with an efficiency > 85% but are still very expensive. The size of restart and mesh files is very large, post-processing is complicated and data management becomes near-impossible. 64 billion cells computations go beyond all limits: solver, supercomputer, MPI, file size, post-processing, data management. For these reasons, we barely managed to execute more than a few iterations. Over the last 30 years, neptune_cfd HPC capabilities improved exponentially by tracking hardware evolution and by implementing state-of-the-art techniques for parallel and distributed computing. However, our last findings show that currently implemented MPI/Multigrid approaches are not sufficient to fully benefit from pre-Exascale system. This work allows us to identify current bottlenecks in neptune_cfd and to formulate guidelines for an upcoming Exascale-ready version of this code that will hopefully be able to manage even the most complex industrial-scale gas–particle systems. [Display omitted] • 8 and 64 billion-cells computations of a fluidized bed at industrial scale • neptune_cfd code (based on Euler-nfuid approach) scalability and performances. • HPC up to 286,000 cores on recent and powerful supercomputers. • Identification of limitations bottlenecks and developments on the route of Exascale. [ABSTRACT FROM AUTHOR]

This study introduces the application of a spiral structure in pipeline transportation to enhance the pipeline capacity of a slurry shield circulation system. A numerical model of solid–fluid coupling in a pipeline with a double spiral structure was established based on computational fluid dynamics and the discrete element method (CFD–DEM) theory, and its validity was confirmed through comparison with experimental data. The characteristics of the spiral pipeline were evaluated by comparing them with those of a conventional smooth straight pipeline. A multi-objective optimization method for determining the structural parameters of a spiral pipeline in a slurry shield circulation system is proposed using the Kriging surrogate model. The optimized design of a spiral pipeline was demonstrated through a specific project, and the impact of the main structural parameters on the slurry transport characteristics of the pipeline was analyzed. The results indicated that the optimized structural parameters led to an 18.65% increase in the average flow rate of the slurry and a 19.13% reduction in the accumulation of stones in the pipeline. [Display omitted] • The Spiral pipeline with transverse protrusion is applied to slurry-water circulation pipe. • The slag carrying performance of pipeline was evaluated by CFD–DEM method. • The relationship between the structure parameters and the slag carrying performance of the pipeline is studied. • The optimization process is used to optimize the structural parameters. [ABSTRACT FROM AUTHOR]

In the present work, the hydrodynamics behavior of a 3D small-scale cold flow modeling of a gas-solid tapered fluidized bed is evaluated with the Eulerian-Eulerian two-fluid modeling (TFM) approach. The sensitivity of different modeling parameters, including lift and virtual mass forces, viscous force, gas-solid drag force, granular temperature, granular viscosity, granular pressure, particle-wall specularity coefficient, particle-particle restitution coefficient, and particle-wall restitution coefficient, are systematically investigated to optimize the performance of the present numerical model. The results from different sensitivity analyses reveal that the gas-particle drag force is a more important force to resolve the correct time-averaged axial and radial solids holdup profiles of the tapered fluidized bed than the other investigated parameters. The highest accuracy possible from simulations is achieved from the Gibilaro drag model followed by the Arastoopour and EMMS/bubbling models. In contrast, all other drag models over-predict the gas-particle interaction force. The assessment of the lift and virtual mass forces, viscous force, granular temperature, granular viscosity, granular pressure, and particle-wall restitution coefficient results reveal that these parameters are less critical for the numerical simulations of the tapered fluidized bed than the gas-solid drag force. However, the assessment of particle-wall specularity coefficient and particle-particle restitution coefficient reveals that adjusting these parameters in the numerical simulations is helpful to achieve a better agreement between the experimental data and model results. For the higher gas flow rate, the current work shows that a better agreement can be achieved by tuning the parameter values in the standard sub-models than the previously published TFM studies. Meanwhile, for the lower gas flow rate, the accuracy of the present work is slightly lower than the previously published work but acceptable with the experimental measurements. The current work has an advantage over the previously published work in terms of lower computational effort by using the simplified geometry and mean particle diameter assumptions. [Display omitted] • We simulated a 3D tapered fluidized bed reactor using the TFM approach. • We performed the sensitivity analysis of key modeling parameters and sub-models. • Drag force has a much greater impact on the hydrodynamics than the other forces. • We implemented the BVK, EMMS/bubbling, and Arastoopour drag models through UDFs. • We optimized the performance of the TFM based on its sensitivity analysis. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydraulic conveying of coarse grains through a narrow 90° elbow is investigated • Resolved CFD-DEM simulations were performed by using the Immersed Boundary method • We found the maximum amount of particles entrained by a given water flow • For low velocities, particles settle in the elbow forming a granular lattice • We show the levels of liquid velocity necessary to carry or destroy the lattice This paper investigates numerically the hydraulic conveying of solids through a 90° elbow that changes the flow direction from horizontal to vertical, in the very-narrow case where the ratio of pipe to particle diameters is less than 5. We performed resolved CFD-DEM (computational fluid dynamics - discrete element method) computations, in which we made use of the IB (immersed boundary) method of the open-source code CFDEM. We investigate the effects of the water flow and particle injection rate on the transport rate and sedimentation by tracking the granular structures appearing in the pipe, the motion of individual particles, and the contact network of settled particles. We found the saturated transport rate for each water velocity and that a large number of particles settle in the elbow region for smaller velocities, forming a crystal-like lattice that persists in time, and we propose a procedure to mitigate the problem. [ABSTRACT FROM AUTHOR]

Non-uniform sand retention behavior often occurs to the serviced screen deteriorating erosion. However, this phenomenon is poorly understood. This paper presents a numerical study of the sand retention on wire-wrapped screens, with special reference to non-uniform behaviors. This is done by the combined approach of computational fluid dynamics (CFD) and discrete element method (DEM). The validity of the model has been validated for dry and wet sand screen systems. It is used here to study sand retention behaviors at different solid concentrations and particle size distributions (PSD). Via this model, five distinct sand retention modes are identified: No sand retention (Mode I), partial sand retention (Mode II), sand retention with slow sequential bridging (Mode III), sand retention with fast sequential bridging (Model IV) and sand retention with instantaneous bridging (Mode V). Modes II and III belong to non-uniform sand retention, which develops strong local flows that induce local erosion or hot spot on the screen. A phase diagram is introduced to predict these five modes and their transition with respect to solid concentration and PSD. Additionally, the predicted flow and force structures are analyzed in detail. The results indicate that the bridging over a slot heavily relies on the particle accumulation on the screen. A new screen with a converging slot configuration is proposed to improve this particle accumulation. This improvement helps develop uniform sand retention on the screen. [Display omitted] • Sand retention behavior over sand screen is studied by a CFD-DEM model. • Five retention modes occur in various sand concentrations and size distributions. • A phase diagram is introduced to predict sand retention modes and their transition. • Undesirable non-uniform sand retention mode is particularly analyzed. • A new screen is proposed to mitigate non-uniform sand retention behavior. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel Hydrocyclone with circular rings introduced • CFD simulations with LES-WALE turbulence model was established to provide accurate predictions • Extensive CFD simulations done to predict performance improvements in novel hydrocylone • Attractive reductions in the bypass of fines and sharper classification observed • Number, location, size, orientation can be optimization variables for further improvements Hydrocylones offer a process intensified environment for rapid, high-throughput and relatively sharp particle classification or phase separation. One of the main performance limitations of hydrocyclone is bypassing of fines to the underflow. To address this limitation, a novel design modification of fitting thin concentric rings to the cylindro-conical section has been proposed. The Computational Fluid Dynamics (CFD) modeling based methodology has been adopted to validate the hypothesis. Predictions using Realizable k - ε , Reynolds Stress Model (RSM), and Large Eddy Simulation Wall Adopting Local Eddy viscosity (LES-WALE) turbulence models has revealed that LES-WALE matched better with the experimental observations. The experimental data included overall performance parameters and detailed observations of axial and tangential velocity profiles across the hydrocyclone. The validated CFD model and the methodology was then used to predict the behavior of the proposed designs. They established that the modifications held promise in reducing the bypass with additional benefits of sharper separation curve and finer D 50. [ABSTRACT FROM AUTHOR]

The particle manipulation technology based on standing surface acoustic waves (SSAW) has been widely used with high efficiency and low consumption. However, it is difficult to study particle motion at the microscopic scale with experimental methods and conventional continuous methods. In this paper, computational fluid dynamics (CFD) and the discrete element method (DEM) are used to describe the fluid-particle flow, and the effect of the acoustic field is calculated according to Gorkov's theory. The established model is validated by the particle separation in micro-channel under SSAWs as the simulation results are in good agreement with experiments in publication. The consistency between the numerical simulation results and the experimental results in separation time and separation distance confirms the merits of model. The particle motion, space distribution, velocity field, force analysis and particle collision have been conducted thoroughly to reveal the mechanism of the separation. • CFD-DEM can simulate particle separation by SSAW with high accuracy. • Drag force and acoustic force compete each other to determine the particle motion. • The particle experiences the maximum acoustic force at x = ±37.5 μm. [ABSTRACT FROM AUTHOR]

Understanding fluid flow in granular materials is essential for many engineering applications, including petroleum recovery, groundwater movement and embankment stability. This study investigates the influence of particle angularity on permeability and fluid-particle interaction forces. A random shape generator based on spherical harmonics is used to create irregular-shaped particles with different levels of angularity. Granular packings of uniformly sized (monodisperse) particles are then constructed with the discrete element method (DEM), and pore-scale computational fluid dynamics (CFD) simulations are used to determine the flow fields and the resulted fluid-particle interaction. The more angular particle assemblies thus generated are less permeable, and their fluid-particle interaction forces are higher. However, angularity has limited influence on flow rate distribution and flow tortuosity. The influence of angularity is localized. An increase in angularity generates a larger variance of the pressure distribution on the particle surfaces, thus increasing the pressure component of the fluid-particle interaction force. [Display omitted] • A framework to generate dense packings of angular particles is proposed. • Flow in packings of uniform angular particles is simulated with pore-scale CFD. • Influence of particle angularity on permeability is quantified. • Detailed statistical analysis is performed on fluid-particle interactions. • Particle-to-particle variance of fluid-particle interactions is analyzed. [ABSTRACT FROM AUTHOR]

Direct impingement (DI) erosion testing of steel and cobalt-based alloys is conducted with particles entrained in air and water. The tests are performed using 75- and 300-μm silica particles with three particle velocities and five impact angles. The mass loss results are used to develop an empirical equation that contains an explicit exponential term for the particle size effect. The erosion equation obtained from the gas jet experiments is implemented into a CFD solver with Lagrangian particle tracking for the liquid-submerged geometry. The CFD-based erosion predictions agree fairly with the experimental measurement for both particles. Strong effect has been observed for the exponential correction term in the erosion equation for liquid-solid flow cases; particularly with small particles at low impact velocities. [Display omitted] • Dry and wet direct impingement tests have been performed. • Particle size of 75 μm and 300 μm have been used. • Erosion of cobalt-based alloys have been characterized and compared with that of steel. • Experiment based erosion equation has been developed for particle size variation. • Computational Fluid Dynamics (CFD) model predicts erosion compareble to test measurements. [ABSTRACT FROM AUTHOR]

The coefficient of restitution (CoR) is an empirical parameter in dense gas-particles computational fluid dynamics (CFD) by means of kinetic theory of granular flow (KTGF). A great sensitivity of CoR on predictions was found because of the existence of multiple collisions of particles in fluidized beds. In present study, an empirical correlation of granular CoR is proposed using a coupled KTGF of Euler granular phase and the discrete element method (DEM) of Lagrange discrete particles. The CoR is calculated using statistical methodology according to relative velocity of two colliding discrete particles. The granular CoR is computed from granular volume fractions, indicating that the multiple collision effects on momentum conservation over collision at high granular volume fractions. The granular constitutive equations for the transport coefficients are solved according to granular CoR. The simulated bed expansions agreed with experimental measurements. The predicted granular pressure and viscosity are compared with measured data. [Display omitted] • The CFD-kinetic theory of granular flow-discrete element method is proposed. • The granular CoR is correlated as a function of granular volume fractions. • The expanded bed height using varied granular COR agrees with measured data. • The predicted granular pressure and viscosity are compared with experimental data. [ABSTRACT FROM AUTHOR]

The key to the layout of the roof horizontal long drilling hole is to accurately locate the range of gas-conducting fracture zone. In this paper, the discrete element method (DEM) is firstly adopted to quantitatively simulate the porosity distribution in goaf from a microscopic perspective, with the 6306 working face of the Tangkou coal mine as an engineering example. Then, the three-dimensional porosity distribution data is extracted and converted into a two-dimensional array form, which was verified by the mathematical model established by previous work. After that, combining the DEM data and mathematical model result, user-defined function (UDF) codes are written and imported into computational fluid dynamics (CFD) software to simulate the gas distribution in the goaf before and after the drilling of the working face. The results show that the gas in goaf is mainly distributed in the upper position after drilling, and the proportion of gas in the bottom position is largely reduced. The boreholes arrangement in the gas-guiding fissure zone is reasonable effectively reducing the gas concentration in goaf. [Display omitted] • Analysis of the gas-guiding fissure zone from a macro and mesoscopic perspective. • The model porosity data set is obtained based on the DEM simulator. • The porosity data into a two-dimensional array and import it into CFD. [ABSTRACT FROM AUTHOR]

[Display omitted] • Analytical solution to one-dimensional compressible flow in packed beds. • Regime maps with friction, heat exchange, and change in porosity considered. • Limits of the commonly-adopted incompressibility assumption identified. • CFD-DEM model presented for subsonic compressible flow. We present regime maps for subsonic flow in dense gas-particle systems, which demarcate regions of compressible and (effectively) incompressible flow. These maps should aid researchers and industrialists in selecting the appropriate modeling approach, as well as in verifying numerical solvers. Demonstrating compressibility at Mach numbers lower than 0.3, we show that this commonly used criterion is insufficient for flows in porous media. For M < 0.1, systems dominated by heat exchange experience compressible effects at a fixed value of a dimensionless system parameter, while critical parameters in an adiabatic system can be assessed using a simple relation of the Mach number. Ultimately, we present a model based on computational fluid dynamics and discrete element method (CFD-DEM) allowing efficient calculation of subsonic compressible gas-particle flows. [ABSTRACT FROM AUTHOR]

The erosion-induced failure of elbows commonly occurs in the pipeline transport industry. In this study, a computational fluid dynamics (CFD) method was adopted to study the erosion of air-solid elbows. The results show that when the working conditions in the air-solid elbow are changed, there are three types of erosion morphologies: the concentrated-exit type, transition type, and "V" type; the erosion morphology is mainly related to the trajectory of the particles. An arc-shaped diversion erosion-inhibiting plate structure (ASDEIPS) is proposed to reduce the erosion rate for elbows with transition type or "V" type erosion morphologies by up to 41%. Another advantage of the ASDEIPS is its ability to improve the flow field of the elbow under any working condition and to reduce the pressure drop, turbulent kinetic energy, and turbulence dissipation rate of the elbow. [Display omitted] • An arc-shaped diversion erosion-inhibiting plate structure (ASDEIPS) is proposed. • Compared with elbow, the erosion rate of ASDEIPS can be reduced by up to 41%. • The pressure drop and turbulence of ASDEIPS are always lower than that of elbow. [ABSTRACT FROM AUTHOR]

The study's main goal, as reported in this research paper, was to investigate the gas–solid flow behaviors in a twin cyclonic fluidized-bed combustor (T-FBC) in swirling mode under a range of operating conditions. Silica sand in three size ranges, 300–500 μm, 500–710 μm, and 710–1000 μm, with 1700 kg/m3 solid density was used as the bed material in the study's experimental tests and its computer simulations. The Eulerian–Eulerian approach for two-phase fluid flows was selected to investigate the cold hydrodynamic characteristics of gas–solid particles, at a constant ambient temperature, in the fluidized-bed combustor. The three different turbulence models; the standard k-ε model, the renormalization group (RNG) k-ε model, and the Reynolds Stress Models (RSM) were studied in order to select the most appropriate model. Finally, the RNG k-ε turbulence model was applied in all simulations for both phases of our work. The computational simulations were performed using the same parameters and operating conditions as in the experimental tests, with the validity of the computational simulations thus experimentally verified. In the simulation results, it was shown that the increasing size of the bed particles, the solid hold-up tended to decrease, the time duration for initializing full-bed fluidization increased, and the bed fluctuation frequency decreased. When increasing excess air (EA), the simulation results showed the opposite trend. The secondary to total air ratio (S / T) had substantial effects on time duration to initialize bed fluidization and the bed fluctuation frequency in the swirling fluidized bed; however, it had slightly effects on the radial solid hold-up and radial solid velocity in the dense bed region. [Display omitted] • The Δ p-u diagram for all particle size ranges exhibited four operational regimes. • Solid hold-up profiles show symmetric radial distribution with peak at the center. • Solid Bed required greater time to attain full fluidization when size increases. • Smaller particle size has higher fluctuation levels than the bigger particle size. • EA and S/T had substantially affects to the fluidization behavior. [ABSTRACT FROM AUTHOR]

Liquid bridges between wet particles affect pneumatic elbow erosion, but the associated mechanism remains unclear. This paper presents a numerical study of elbow erosion using a combined approach of computational fluid dynamics and discrete element method facilitated with erosion and capillary force models. Particle dynamics and the elbow erosion location, depth and ratio are analysed in detail. The results show that wet particles tend to adhere to the inner wall of the elbow during transport under the effect of liquid bridges. This phenomenon forms a particle layer that covers the impact area, thereby substantially decreasing both the erosion depth and ratio of the elbow. A U-shaped erosion scar is observed in the extrados of the elbow when conveying wet particles. Additionally, the effects of gas velocity and moisture content on particle flow and elbow erosion are revealed to clarify the differences between dry and wet particles. [Display omitted] • Flow behavior and elbow erosion of wet particles are studied by a CFD-DEM model. • Wet particles tend to adhere to the inner wall of the elbow reducing its erosion. • A U-shaped erosion scar is observed in the extrados of the elbow for wet particles. • Effects of gas velocity and moisture content on particle flow and erosion are revealed. • The result elucidates differences between dry and wet particles. [ABSTRACT FROM AUTHOR]

The hydrodynamics of a circulating fluidized bed (CFB) combustor were investigated by conducting experiments on a 100 kW th CFB test rig and a 3D simulation using a computational particle fluid dynamics numerical scheme. Two empirical models were evaluated for estimating the solids volume fraction of the reactor by comparing the experimental and simulation results. The decay coefficients (a and K for the models) were derived from the simulation results to predict the decay of the axial solids volume fraction in the riser. From the viewpoint of accuracy, the two exponential functions model outperformed the one exponential function model. Empirical models for estimating the core-annulus flow structure in the transport zone were also investigated. Two existing empirical correlations reasonably predicted the wall layer thickness of the test cases except when the superficial velocity was 6.2 m/s. Under such high-velocity conditions, the empirical models overestimated the wall layer thickness by more than 100%. [Display omitted] • A back-mixing coefficients a and K were obtained from a small and narrow CFB reactor with experiment and 3D simulation. • The empirical model with two exponential decay functions better predicts solids volume fraction in both splash and transport zone. • Under high-velocity conditions, two existing empirical models overestimated the wall layer thickness. [ABSTRACT FROM AUTHOR]

Laminar fluid-particle flows in bend geometries are present in many industrial, pharmaceutical, and biomedical applications. Particle deposition has been studied extensively; however, little attention has been paid to the effect of particle sedimentation on particle position and deposition in different pipe geometry combinations. This study presented a comprehensive analysis of sedimentation effects on particle flow behaviour in 90° circular pipe bends of micron particles in laminar pipe flows. Pipe geometry combinations consisted of eight pipe diameters, nine bend radii, and 30 particle diameters in a range of 1 to 100 μm. The results demonstrated the locations of particles that sedimented to the bottom half of the straight pipe section, and the particle positions upstream from the pipe bend entrance, which was no longer in a fully developed profile. These new locations represent the effects of gravity, pulling the particles down. While obtaining these positions can be found through CFD analysis, we proposed an analytical solution to predict the particle trajectory from different release locations that would help to identify the initial particle distribution at locations upstream to the bend, to obviate the need for long upstream straight pipe sections in the CFD analysis. [Display omitted] • The effect of particle sedimentation on pipe geometry combinations was studied. • The study emphasized the sedimentation for micron particles in laminar pipe flows. • Combinations: 8 pipe diameters, 9 bend radii, and 30 particle diameters in microns. • Sedimentation caused particle deposition on the inner wall side of the pipe bend. • To obviate the need for long upstream straight pipe sections in the CFD analysis. [ABSTRACT FROM AUTHOR]

Bends are potentially most problematic in a hydraulic conveying pipeline system. This paper presents a numerical study of hydraulic bends, with special reference to the interaction between pipe orientation and flow regime. This is done by the combined approach of computational fluid dynamics and discrete element method facilitated with a wear model. The validity of the model has been verified by comparing the measured and predicted flow properties and erosion depth. On this basis, three pipe orientations: 0° (i.e. horizontal-vertical bend), 45° (i.e. inclined bend), and 90° (i.e. vertical-horizontal bend) are simulated for the conveying speeds of 1.2 m/s, 2.0 m/s and 4.0 m/s. It covers typical flow regimes in a horizontal pipe. Via the simulation outputs, the bend performance is assessed in terms of pressure loss, conveying instability and bend erosion. The results reveal that the pressure drop and erosion rate differ for various pipe orientations and conveying speeds involving different flow regimes. The acceleration/de-acceleration of the particles exiting the bend does not result in a significant additional pressure. The vertical-horizontal bend has low erosion rates benefiting from cluster formation and low pressure, which is not the case at high conveying speeds. By contrast, the inclined bend gives the highest elevation height and does not suffer significant pressure drop, pressure fluctuation, and erosion rate under all the flow regimes considered. [Display omitted] • Flows and wall erosion of hydraulic bend are studied by the CFD-DEM approach. • Interaction between pipe orientation and conveying speed/flow regime is focused. • Pipe orientation affects flows and bend erosion but mainly at low conveying speeds. • Particle acceleration in a post-bend does not give a large additional pressure loss. • Vertical-horizontal bend has low erosion rates but only at a low conveying speed. [ABSTRACT FROM AUTHOR]